Linear television has been the model of television distribution in the United States since the 1940's. In a linear television model, a broadcaster schedules programs to air at specific times. Consumers can obtain guides, which could be paper or electronic, to determine what program is being aired at a given time for a given source. Consumers can time shift content from a linear distribution source in a number of ways. Consumer electronic devices like VCR's and DVR's allow for the recording of a program at its scheduled time, and playback can be at the time of choosing of the consumer.